Julia is an eleven-year-old only child living in a quiet Southern California suburb. She is observant and shy, finding herself increasingly isolated as she experiences the awkwardness of sixth grade. As Earth's rotation mysteriously begins to slow, she relies on her parents for stability and watches the changing world around her. She processes the global disaster through the lens of her own quiet, personal adolescent struggles.

Seth is a quiet sixth-grader who rides a skateboard and mostly keeps to himself. He deals with personal hardships at home since his mother is suffering from severe breast cancer. He captures Julia's attention from afar, standing out from the louder, more boisterous boys at school. He demonstrates a gentle, thoughtful demeanor in contrast to the panic surrounding the planetary crisis.

Helen is Julia's mother and a former actress who has settled into suburban domesticity. She is a natural worrier who reacts to the news of the slowing by immediately stockpiling emergency supplies, seeking to control her environment. Her anxiety over the global disaster exacerbates existing cracks in her marriage and personal well-being.

Joel is Julia's father and a doctor who specializes in delivering high-risk babies. In contrast to his wife's panic, he responds to the global crisis by attempting to maintain an illusion of normalcy. He tries to dismiss the severity of the planetary events to soothe his family, sometimes bending the truth to shield them from bad news.

Sylvia is a free-spirited piano teacher who lives across the street from Julia's family. She embraces a naturalist lifestyle, often playing the piano barefoot while wearing chunky turquoise jewelry. She approaches the planet's shifting rotation with a philosophical acceptance, viewing the disaster as a natural consequence of humanity's environmental abuses.

Gene is Julia's eccentric eighty-four-year-old grandfather. He stubbornly refuses to update his lifestyle, remaining the only resident of an older house surrounded by a modern housing development. He views the planetary deceleration with heavy skepticism and suspects it might be an elaborate government conspiracy. He keeps numerous antique trinkets hoarded inside his home.

Hanna is Julia's longtime best friend who comes from a large Mormon family. She provides a vital source of companionship for Julia. The sudden news of the planetary crisis prompts her family to hastily relocate to Utah, creating a sudden and painful social void in Julia's daily life.

Gabby is a childhood friend of Julia's from the neighborhood. She is entering an intense rebellious phase marked by smoking cigarettes and wearing goth clothing. Her behavior leads her parents to transfer her to a strict Catholic school, widening the gap between her and Julia.

Michaela is a popular, rapidly maturing girl in Julia's class. She flaunts her burgeoning teenage independence, wearing training bras and hosting coed parties. She represents the mainstream adolescent social circle from which Julia feels totally excluded.

Daryl is a boisterous middle schooler who waits for the bus with the neighborhood kids. He acts as a schoolyard bully, publicly humiliating his classmates to assert his own social dominance during an already stressful time.

Chip is a goth teenager who lives near Gene's house. Despite their significant age difference, he forms an unlikely bond with the elderly man over their shared distaste for the modern housing development surrounding them.

Tracey is a Mormon student at Julia's middle school. When Hanna returns from Utah, Tracey quickly pairs off with her, wearing matching outfits and solidifying Julia's exclusion from her former best friend's life.